[mou] Strange robin behavior

My mom just emailed me with this description of some
weird robin behavior. We were wondering if anyone has
any ideas why she is doing this?
"I heard a persistant pounding noise. It sounded like
someone hitting on a board just outside my bedroome
window. there was a robin trying to fly into the
window! It flew up about 6 to 12 inches and then out
and back to the sill. My moving the curtains did not
scare it. I had to put my hand right up to its face
to scare it away! I figured all that thumping wasn't
good for it. I made coffee and there was the noise
again, but not in my bedroom, but in the guest room
window, doing the same thing. I had to wave at it
again as just opening shades and curtains did not
startle it. It was the same robin - one of its tail
feathers was turned up or out a bit and was white.
It's mate was close by in the tree but didn't do that.
It kept coming back to those windows at least a dozen
times, even when I was at the computer!! What do you
think it was doing?"
We're both curious and I thought I'd see if anyone has
any ideas...
Jenn